Polymerization of alkylene oxides using a binary catalyst system of zirconium tetraisopropoxide and an organometallic compound



United States Patent Ofiice 3,436,360 Patented Apr. 1, 1969 POLYMERIZATION OF ALKYLENE OXIDES USING A BINARY CATALYST SYSTEM OF ZIRCONIUM TETRAISOPROPOXIDE AND AN ORGANOME- TALLIC COMPOUND Hideo Tomomatsu, Austin, Tex., assignor to Jefferson Chemical Company, Inc., Houston, Tex. N Drawing. Filed Aug. 21, 1967, Ser. No. 661,840 Int. Cl. C08g 23/14 U.S. Cl. 260-2 6 Claims ABSTRACT OF THE DISCLOSURE High molecular weight polymers having a high degree of crystallinity are obtained from the polymerization of cyclic alkylene oxides employing a binary catalyst system consisting of an organometallic compound of the formula MZX wherein M is a metal of Group II or III, Z is a hydrocarbon; X is hydrogen, halogen, Z, alkoxy or aryloxy, and y is an integer equal to the valence of M and zirconium tetraisopropoxide. Cyclic alkylene oxides employed are those containing oxygen-carbon rings consisting of one oxygen atom in a ring with two or three carbon atoms.

BACKGROUND OF THE INVENTION This invention is concerned with the polymerization of cyclic alkylene oxides using a binary catalyst system of an organometallic compound and zirconium tetraisopropoxide.

The polymerization of alkylene oxides is well known. For many years low molecular weight polymers have been obtained by the polymerization of alkylene oxides in the presence of alkaline catalysts. More recently, efforts have been made to obtain tough, solid polymeric alkylene oxides having molecular weights of one million or more.

When alkylene oxides having side chains, such as propylene oxides and epichlorohydrin, are employed, the polymerization may yield both stereoregular and stereoirregular polymers, depending mainly on the polymerization catalyst employed. Stereoregular polymers are crystalline, while stereoirregular polymers are amorphous. For some purposes, crystalline polymers are more desirable. Thus, at times it is important not only to obtain polymers of extremely high molecular weights but also to obtain polymers containing a high percentage of stereoregular polymer.

Organometallic compounds of the type employed in my catalyst system (specifically, diethyl zinc) have been reported to have no catalytic activity in the polymerization of oxides when used alone (I. Furukawa et al., J. Polymer Sci., 36, 542 (1959)). Therefore it was entirely unexpected that by mixing these organometallic compounds with zirconium tetraisopropoxide, which also exhibts no catalytic activity alone, a high yield of high molecular weight polymer containing a high percentage of stereoregular polymer could be obtained.

SUMMARY OF THE INVENTION I have now developed a method for the polymerization of cyclic alkylene oxides whereby high molecular weight polymers having a high degree of crystallinity may be obtained. In accordance with my method a binary catalyst system of zirconium tetraisopropoxide and an organometallic compound as defined hereinbelow is employed.

DESCRIPTION OF THE PREFERRED EMBODIMENT One component of my catalyst system is zirconium tetraisopropoxide. Commercially available zlrconlum tetraisopropoxide may be employed without the need for purification.

The organometallic compound to be used in conjunction with the zirconium tetraisopropoxide is defined as one having the formula MZX wherein M is a metal belonging to Groups II and III, and preferably Groups II-B and III-A, of the Periodic Table, Z is a member selected from the group consisting of alkyl, cycloalkyl and aryl groups containing from 1 to 18 carbon atoms, X is selected from the class consisting of hydrogen, halogen, Z and alkoxy and aryloxy groups containing 1 to 18 carbon atoms, and y is a whole number equal to the valence of M. This metallic compound will contain at least one alkyl or aryl group and may contain additional such groups or alkoxy, aryloxy, hydrogen or a halogen such as chlorine, bromine, or iodine. Examples of M include magnesium, calcium, strontium, barium, zinc, cadmium and aluminum. Typical examples of Z include methyl, ethyl, phenyl, butyl, hexyl, cyclobutyl, cyclohexyl and tolyl. Z is preferably an alkyl group. In addition to the above groups, X may be hydrogen, chlorine, bromine, iodine, ethoxy, propoxy, butoxy and phenoxy. Especially preferred organometallic compounds are diethyl zinc and triethyl aluminum. Other acceptable compounds include diethyl aluminum hydride, ethyl aluminum dichloride, diphenyl zinc, methyl zinc phenoxide, dilauryl cadmium, triethyl gallium, phenyl cyclohexyl beryllium and dibenzyl cadmium.

The cyclic alkylene oxides that may be polymerized by my process are those containing oxygen-carbon rings in which one oxygen atom is combined with two or three carbon atoms in the ring. The ring carbon atoms may be substituted with alkyl, aryl, cycloalkyl, alkoxy and haloalkyl groups. The most common cyclic alkylene oxides are those containing the three-membered oxirane ring. Examples of such oxides include ethylene oxide, l,2-pm pylene oxide, 1,2-butylene oxide, 12,3-butylene oxide, 1,2- dodecene oxide, styrene oxide, epichlorohydrin and allyl glycidyl ether. A typical four-membered alkylene oxide is 1,3-propylene oxide, commonly referred to as oxetane. Other such cyclic oxides include 3,3-dimethyloxetane, 3,3- diethyloxetane and 3,3-di(chloromethyl)oxetane.

The concentration of the mixed catalyst may be varied from 1 to 20 wt. percent or higher based on the weight of the monomeric oxide. It is preferred to use from about 5 to 10 wt. percent catalyst. The weight ratio of zirconium tetraisopropoxide to organometallic compound in the catalyst may be varied from about 10:1 to 1:10 with the preferred ratio being from about 1:3 to 3:1.

The polymerization may be run at a temperature within the range of 0 to 200 C.; however, it is preferred to employ temperatures within the range of about 25 to about C. To avoid loss of volatile components, the reaction is normally conducted in a closed vessel. Th particular pressure at which the reaction is conducted is not critical, and ambient pressures are enerally employed.

The polymerization reaction should be conducted in a dry, inert atmosphere. A dry, inert solvent is employed. The solvent may be an aliphatic or aromatic hydrocarbon or an ether. Typical solvents include cyclohexane, n-hexane, petroleum ether, pentane, heptane, benzene, toluene, diethyl ether and dipropyl ether.

After the polymerization is complete the catalyst may be quenched by the addition of a suitable amount of a lower aliphatic alcohol, preferably isopropyl alcohol, in solution in an inert solvent as described above. Generally, suflicient alcohol is used to react with both components of the catalyst system. The presence of the quenched catalyst in the polymer does not adversely affect the polymer properties. It is also possible to add a 3 small amount of antioxidant (usually 0.3 to 3.0 wt. percent based on the monomeric oxide) in solution in a solvent to increase the stability of the polymer.

To demonstrate the unexpected synergistic effect shown by my two-component catalyst system, propylene percent based on the weight of oxide of a binary catalyst system of (A) zirconium tetraisopropoxide with (B) an organometallic compound having the formula oxide was polymerized using zirconium tetraisopropoxide MZXY1 alone, diethyl zinc alone, and a combination of zirconium wherein M is a metal from Groups II and III of the tetraisopropoxide with diethyl zinc, These polymeriza- Periodic Table, Z is selected from the class consisttions were conducted in cyclohexane solvent at 80 0 ing of aryl, cycloalkyl and alkyl groups containing for a period of 24 hours. The results of these experiments from 1 to 18 carbon atoms, X is selected from the are summarized in Table 1. The intrinsic viscosity of class consisting of hydrogen, halo en, Z and alkoxy the polymers was observed in toluene at 25 C. Fracand aryloxy groups containing 1 to 18 carbon atoms tionation of the polymer to determine the crystalline and y is an integer equal to the valence of M, the content was carried out by dissolving the polymer in weight ratio of zirconium tetraisopropoxide to orsixty times its weight of acetone and precipitating the ganometallic compound in the catalyst mixture being crystalline fraction by cooling the solution to -45 C. within the range of from 10:1 to 1:10. TABLE 1 Cone. based Total polymer Crystalline Run No. Compound on propylene fraction, oxide, Yleld, Intrinsic Avg. mol percent percent percent; viscosity wt.

1 Zirconium tetralsopropoxide 8. 52 5 2 Diethylzlnc, 5.0 0 3 Zirconium tetraisopropoxlde plus di- 8. 52+3. 2 55 2. 7 0. 589x10 49 ethyl zinc.

My invention will be further illustrated by the follow- 5 2. A method as in claim 1 wherein M is a metal from i l Groups 1113 and IIIA of the Periodic Table.

Example I 3. A method as in claim 2 wherein the temperature is within the range of to 150 C., the catalyst con- Commercially available zirconium tetraisopropoxlde ce t ti i i hi the range f 5 to 10 wt percent (4.26 grams) was placed in a 1,000 ml. Pyrex glass P based on the weight of oxide and the weight ratio of sure bottle under dry nitrogen. To this was added 200 zirconium tetraisopropoxide to organometallic comgrams of freshly distilled, dried cyclohexane, and the poundiswithintherangeof3;1to1:3. mixture was stirred under airtight conditions to a slightly 4. A method as in claim 2 wherein Z is an alkyl group turbid mixture. A 25% solution of diethyl zinc in hepcontaining 1 to 18 carbon atoms. 7 tane (6.41 grams) was added, and after complete miX- 5. A method as in claim 4 wherein the organometallic ing 50 grams of freshly distilled propylene oxide was compound is diethyl zinc. added. The pressure bottle was closed by a stainless steel 6. A method as in claim 5 wherein the temperature cap equipped with a Teflon O-ring and was subjected to is within the range of 25 to 150 C., the concentration shaking in an oil bath at 80 c. for 24 hours. The reof the catalyst mixture is between 5 to 10 percent action mixture was mixed with 50 m1. of cyclohexane the Weight of PXide f the g t ratio f which contained 0.25 gram of isopropyl alcohol and 0.25 zu'comum tetralsopmpoxlde t0 dlethyl c is between gram of dibutyl-para-cresol. After this mixture had been 3:1 and left standing for several hours, it was poured on alumi- References Cited num foil to allow the solvent to evaporate. In this way UNITED STATES PATENTS there was obtained 29 grams of a white, tough, rubbery 2 956 959 10 19 0 Better. material. The intrinsic viscosity of the polymer determined in toluene at 25 C. was 2.7. The molecular OTHER REFERENCES weight calculated from the intrinsic viscosity was Journal of Polymer Science, 47 (XLVH) 0589x10 50 I claim: 1. A method for the polymerization of cyclic alkylene WILLIAM F Pnma'yPxammer' oxide having an oxygen-carbon ring in which the oxygen PERTILLA Asssmm Exammeratom is joined with 2 to 3 carbon atoms in the ring, which us CL comprises mixing said oxide at 0 to 200 C. in a closed vessel and in an inert atmosphere with from 1 to 20 wt. 

